Coherer.



c. FV. FRANK.

COHERER.

APPLICATION mm )une lo. |914.

vPatented Jan. 4, 1916.

Z SHEETS-SHET l.

F Frank H15 Aptorneg.

C. F. FRANK.

COHERER.

APPucATloN FILED JUNE lo, |914.

1,167,163, Patented Jan. 4,1916.

2 SHEETS-SHEET' 2.

Witnesses: lm/entor:

C rosb F Frank, www

. To all whom it may concern.'

i UNITED STATES PATENT OFFICE.

CROSBY FIELD. FRANK, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK..

COHERER.

Specification of Letters Patent.

Patented Jan. 4, 1916.

Application led .T une 10, 1914. Serial No. 844,194.

Be it known that I, CROSBY FIELD FRANK, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certaln new and useful Improvements in Coherers, of which the following is a speciication.

My present invention relates to improvements in coherers of the type which have largely been employed in wireless telegraphy. The present device while adapted for use in that connection is especially suit able for use with signaling or indicatingI apparatus for electrical distribution systems, such for example as that described in Patent No. 1,062,083, issued to Elmer E. F. Creighton on May 20, 1913. Coherers of this type as ordinarily constructed have consisted of a straight tube containing two electrodes with a mass of small metallic particles between them. Thismass normally has a comparatively high resistance but when an electrical potential is impressed upon it its resistance decreases and a greatly increased current flows between the electrodes which are connected to a constant voltage source of direct current. "When the exciting potential is withdrawn the resistance of the mass does not decrease to its original value but some means for shaking the particles to effect a rearrangement thereof is necessary in order to restore the mass to its original high resistance. With the materials heretofore used the decrease of the resistance of the mass has been more or less gradual with increase of the applied otential. For the successful application ofP a coherer to signaling or indicating apparatus for use in connection with electrical distribution systems, however, it is desirable that the material used should have a sharp critical voltage at which the resistance suddenly decreases and permits a largely increased current to flow to operate lthe desired apparatus. It is also essential that the critical voltage shall not vary to any great extent after long continued operation of the coherer. I have discovered that by the use of granules of magnetic material, preferably nickel, properly prepared I am able t0 construct a coherer which has a remarkably sharp critical voltage and in which the critical voltage remains practically constant as long as the a paratus is used. Oneconvenient method o preparin the granules consistsin reducing the oxi of the metal by means of hydrogen at a temperature at which the particles are partially sintered together. The resulting product is crushed in order to secure particles of the desired size and the granules resulting have a dull, gray appearance, are porous and have a large number of sharp projections scattered over their surface. These granules are substantially free from oxid and if placed in a coherer in this condition will gradually ac- .quire an oxid coating and the critical voltage will consequently rise. After a certain time, however, their 'condition vbecomes stable and the critical voltage will then remain constant. If it is desired to produce a coherer having a higher critical voltage than may be conveniently obtained in this way the `granules may be given a thicker coating of 'oxld by heatlng them to a high temperature in the'presence of oxygen. For the successful operation the mass should be thoroughly decohered after each operation. By improvements in the shape of the tube and the decohering apparatus I have been able to produce a coherer in which a thorough decoherence is absolutely certain.

My invention will best be understood by reference to the following description taken in connection with the accompanying drawing, in whichi Figure 1 is a view in perspective of the complete coherer; Fig. 2 is a vertical cross section thereof; Fig. 3 is a vertical crosssection taken through a plane at right angles to thatJof Fig. 2; Fig. 4 is a diagram showing one of the numerous methods of connecting my coherer to a lightning arrester discharge alarm; and Fig. 5 shows volt-ampere characteristics of ordinary nickel filings and nickel granules such as used in my coherer.

In the form here shown my coherer comprises a forked tube 1 having two vertical prongs 2,'2, in each of which an electrode 3 i's placed. The granules of magnetic material fill each of 'the branches of the tube above the electrodes and extend well up into the central tube so that there is a continuous mass of granules between the two electrodes. Flexible Washers 4 attached to the electrodes as shown prevent the granules from dropping out of the tube. f

As decohering means I employ a solenoid 5 surrounding the upper part of the coherer.

When current Hows in this solenoid the"y Wh en there and drawn up into the main tube. The apparatus is preferably so arranged that when the path of current between the electrodes is interrupted, current in the solenoid is alsoA interrupted and the granules drop back to the normal position. The shape of the coherer tube insures that the mass of granules in rising and falling shall be thoroughly shaken so that there is Ano possibility for them to rise and `fall as a single mass and thus fail to be thoroughly decohered. tI am aware that electro-magnetic means have heretofore been used to raise magnetic coH hei-er material and thus decohere but in all such devices the arrangement has been such that the cohering material may rise and fall as a single mass without any change in the relative positions of the separate particles. As a result decoherence is more or less imperfect and the critical voltage at which such a coherer breaks down not constant.

Various ways may bedevised for conveniently mounting the different parts of my device. As here indicated the soleno-id is supported by brackets 6 and 7 attached to asuitable support 8. The coherer tube is held in operative relation to the solenoid by means ot' tbe threaded rod 9 which passes through the metal cap l0 on the upper end ot the tube and is fastened to the strap 1l on the bracket 6 by means of thumb screws l2. By means ot' these thumb screws the cohcrcr tube may be raised and lowered to vary the length of the current pathxthrough the granular n'iatcrial between the electrodes. "the electrodes are rigidly secured to the blo( ,Si oi insulating material which is fastened to the support 8. Suitable terminals 14 for the coherer may be provided upon the block lil. inasmuch as the critical voltage cf the fohercr is dependent upon the dis tance between electrodes the adjustability ol the tube allows of its use with various critical voltages ais desired.

ln Fig. t l have illustrated one ot'thc numerous applications oi my improved coherer. ln this case the coherer l5 is con-- nected through the condensers ll to two points in the ground connection 1T ot the aluminum arrester 18. This arrester is separated from the distribution system by a` horn gip l?) which may be short circuited through the resistance 2() in fri-der to cliarge the alumix'nun cell whenever necessary. T he operating voltage for the co-herer is supplied by the direct current mains 2l, a potentiometer arrangement 2:2 being provided to obtain any oi'ierative voltage desired. is a high voltage impressed upon the ground leg of the arrester, due either to an arcing over of the spark gap or the charging of the arrester the coherer isto actuatei lthe relay 23. This'closes the circuit of the .bellthus causing it to .ring at "cohered allowing current to HOW the same time close the circuit containing the solenoid 24 and the magnet 25 of a suitable counter. This lifts the particles away from the coherer electrodes and thus opens the circuit cf relay 23. This opens the bell magnet circuit and the solenoid circuit in turn and allows the particles to drop again to their original position. i

In Fig. 5 curve A represents the voltampere characteristic of a coherer using ordinary nickel filings, the ordinates'repre-v senting voltage and the abscissae current. (`urve B is the volt ampere characteristic of a cohere using nickel granules reduced from the oxid by hydrogen. The conditions under which thest curves were obtained as regards the size of particles, Sizefof tube and distance between electrodes were the same in both cases.

What l claim as new and desire to secure by Letters Patent of the llnited States, is

l. The combination in a coherer of a vertical tube comprising a main portion and two branches at its lower end, an electrode in each branch and a mass of metallic granules filling said branches above said electrodes and a part of the main portion of the tube.

2. The combination in comprising a main branches, an electrode in each of said branches, a mass of linely divided magnetic material in Said tube between said electrodes and meansfor withdrawing said magnetic material from contact with said electrodes.

3. The combination in a coherer ot a tube comprising a ma in portion and two branches, an electrode in each of said branches, a mass of finely divided magnetic material in said tube between said elecu trodes and a solenoid surrounding said tube.

l. rlhe combination in a coherer of a tube of insulating :nate 'ial comprising a main portion and two branches. a stationary electrode in each of said branches. a mass of inetallic granubs in said tube between said electrodes, means for moving the tube with respect to the electrodes to vary the distance between aid electrodes through said metallic mass. and a solenoid for withdrawa coherer of a tube portio-n and two ing said metallic granules from contact with Said electrmles.

The combination in a coherer of a ver- 'tical tube comprising a main portion and two branches at its lower end, an electrode. extending into each of said branches, a mass of metallic granules in said tube between said electrodes, means for lifting said metallic mass from contact with said electrodes.

6. The combination in a coherer of a Ycertical tube comi'irising a main portion and two branches at its lower end, a stationary electrode in each of said branches. a mass of metallic granules in said tube between said electrodes, and means for raising said tube to vary the distance between said electrodes through said metallic mass.

7. A coherer comprising a container of insulating material, electrodes therein, and a mass of granular material between said electrodes having a sharp critical voltage.

8. A coherer comprising a container of insulating material, electrodes within said container and a mass of metallic granules between said electrodes having ,a high resistance for all voltages impressed thereon below a certain predetermined critical'voltage.

9a A coherer comprising a container o insulating material, electrodes therein and a mass of metallic granules between said electrodes, the material of which said granules are composed being such that the volt ampere characteristic of the device has a sharp bend therein.

10. A coherer containing metallic granules of magnetic-material made by reducing the oXid of the metal at a temperature at which it is partially sintered. 11. A coherer containing nickel granules made by reducing nickel oXid by means of hydrogen at a temperature at which it is `parially sintered.

12. Coherer material consisting of porous nickel granules. l

13. Coherer material consisting of porous granules of magnetic material.

14. Coherer material consisting of porous granules of partially sintered magnetic material.

15. Coherer material consisting of porous nickel granules partially sintered.

16. Coherer material consisting of porous, partially sintered, oXid coated nickel granules.

. 17. Coherer material consisting of porous oxid coated granules of partially sintered magnetic material.

18. Coherer material consisting of porous, partially sintered oXid coated nickel granules having a plurality of sharp projections scattered over .the surface.

19. Coherer material consisting kof porous oXid coated granules of partially sintered ,magnetic material having a plurality of sharp projections scattered over the surface. 20. Cohei'er material consisting of porous oXid coated granules of magnetic material.

2l. Coherer material consisting of porous oxid coated nickel granules.

i 22. Coherer material consisting of porous oXid coated granules of magnetic material having a plurality of projections scattered over the surface.

Copies of this patent maybe obtained for ive cen ts each, ny addressing the oxid'coated nickel granules having a plu,-

' rality of sharp projections scattered over the surface. j

24. Coherer material consisting of porous, partially sintered granules of magnetic material having a plurality of sharp projections scattered over the surface.

Q5. Coherer material consisting of porous, partially sintered nickel granules having a plurality of sharp projections scattered over the surface.

Q6. Coherer material consisting of oxid coated nickel granules partially sintered.

27. Coherer material consisting of oxid coated partially sintered granules of magnetic material.

28. Coherer material consisting of porous granules of magnetic material having a plurality of sharp projections scattered over the surface. I

29. Coherer material consisting of porous nickel granules having a plurality of sharp projections scattered over the surface.

30. Coherer material consisting o oxid coated artially sintered nickel granules having a p urality of sharp projections scattered over the surface.

31. Coherer material consisting of oxid' coated partially sintered granules of magnetic material having a plurality of sharp projections scattered over the surface.

32. Coherer material consisting of partially sintered granules of magnetic material having a plurality of sharp projections scattered over the surface.

33. Coherer material' consisting of partially sintered nickel granules having a plurality of sharp projections scattered over the surface.

3-1. Coherer material consisting of oxid coated nickel granules having a plurality of sharp rojections scattered over the sur ace.

35. goherer material consisting of nickel granules having a plurality of sharp projections scattered over the surface.

36. Coherer material v consisting of partially sintered granules of magnetic material.

37. Coherer material consisting of partially sintered nickel granules.

ln Witness Whereo have hereunto set my hand this 9th day of June, 1914.

CROSBY FELD FRANK.

Commissioner ai Patents.

Washington, D. C. 

